testing equipment for heatstrengthened glass

Use Grazing Angle Stress Polarimeter (GASP)manufactured by Strainoptic technologieshttp://www.strainoptics.com will help to measure the actual surface stress for a glass.This will help you to determine if it is annealed, HS or FT

If you just want to differentiate annealed glass and toughened glass use Toughened glass indicator(TGI) from Merlin Lazerhttp://www.merlinlazer.com/Toughened-glass-indicator-TGI

Gasp will be accurate , but costly.TGI is low cost option.However it is difficult to distinguish heatstengthened and toughened glass using TGI.

Merlin Lazer is easy to use, but Gasp requires some training, before you start using it.